Body odor may be generated in the area under the arms due to a high concentration of sweat glands. While perspiration is odorless, it contains natural oils that can be nutrient source for bacteria living on the skin. These bacteria interact with the natural oils, converting them into odor producing compounds. Antiperspirant compositions contain an active, such as an aluminum salt, that reacts with the electrolytes in perspiration to form a plug in the ducts of sweat glands. The plugs prevent perspiration from exiting the duct, thereby depriving the the bacteria of water and a food source. Antiperspirant compositions may be applied to the skin in either a contact type product form, e.g., a stick or roll-on, or non-contact type product form, such as an aerosol spray. Aerosol spray devices that dispense an antiperspirant composition are known in the art. Various examples are described in U.S. Pat. Nos. 4,152,416; 4,806,338; 4,840,786; 4,904,463; 4,935,224; 5,298,236; 5,605,682; 5,814,309; 7,815,899; EP 674,899; WO 96/04884; WO 2004/014330; and WO 2007/001842.
Many aerosol antiperspirant users desire a product that minimizes the appearance of residue on the skin, has a dry rather than wet feel, has rapid perceived drying, is not sticky, provides a cool/fresh feeling at time of application, provides long lasting wetness and/or odor protection, is provided in a form factor that is easily portable in purses or small bags (as some users may apply the antiperspirant composition more than once a day) and minimizes the gassy cloud that forms during dispensing. While the relative importance/desirability of these characteristics may vary by geographical region and gender and not all users desire all or the same set of characteristics, there appears to be a generally universal desire among aerosol antiperspirant users for one or more of a dry rather than wet feel, minimizing the appearance of residue, and providing long lasting wetness/odor protection or efficacy.
While some currently marketed aerosol spray devices may provide at least some of these characteristics to varying degrees, there are often tradeoffs involved. For example, some currently available aerosol antiperspirant spray devices have relatively high propellant concentrations (e.g., greater than 75% and often greater than 80%). A high propellant concentration dilutes the antiperspirant composition, which in turn may help reduce the risk of clogging within the spray device. However, a high propellant concentration may also produce a large volume of gas upon exiting the spray device resulting in a gassy cloud and/or a turbulent spray. Deposition efficiency (e.g., the amount of antiperspirant active and/or fragrance deposited on skin compared to the amount dispensed) may in turn be reduced due to the large amount of antiperspirant active and/or fragrance lost to the environment via the gassy cloud rather than deposited on the skin. In addition, these spray devices are typically large (greater than 150 ml) in order to accommodate the high propellant concentration and large amount of antiperspirant composition, resulting in spray devices that may be more difficult to carry in small purses and the like. A high propellant concentration may also result in solubilization of liquid fragrance materials into the propellant during storage, resulting in more of the liquid fragrance material being lost to the environment with the propellant rather than deposited on the skin. Many currently available aerosol antiperspirant compositions also incorporate a volatile liquid (e.g., cyclopentasiloxane) as a carrier for the antiperspirant active. The volatile liquid evaporates following application to the skin, resulting in a dry skin feel, but sometimes leaves behind a visible residue (the antiperspirant active) that is subject to flaking and/or transfer to clothing. Flaking (or transfer) of the antiperspirant active may also reduce antiperspirant efficacy. Therefore, there is continuing desire to provide improved aerosol antiperspirant compositions and products.